Tuesday 10 February 2015

34 TOP MySQL Interview Questions and Answers for freshers and experienced pdf

Below are some important MySQL interview questions which are asked in most MNC company interviews for beginners or professionals.

1. What is DDL, DML and DCL?
If you look at the large variety of SQL commands, they can be divided into three large subgroups. Data Definition Language deals with database schemas and descriptions of how the data should reside in the database, therefore language statements like CREATE TABLE or ALTER TABLE belong to DDL. DML deals with data manipulation, and therefore includes most common SQL statements such SELECT, INSERT, etc. Data Control Language includes commands such as GRANT, and mostly concerns with rights, permissions and other controls of the database system.

2. What is primary key?
A primary key is a single column or multiple columns defined to have unique values that can be used as row identifications.

3. What Is Foreign Key?
A foreign key is a single column or multiple columns defined to have values that can be mapped to a primary key in another table.

4. What Is Index?
An index is a single column or multiple columns defined to have values pre-sorted to speed up data retrieval speed.

5. What Is Join?
Join is data retrieval operation that combines rows from multiple tables under certain matching conditions to form a single row.
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